Conventional inflators for inflatable systems, such as airbags, use either a highly pressurized stored gas or a propellant material, typically an azide-based gas generating material, that chemically reacts in a combustion reaction to produce gases.
However, the use of a stored, pressurized gas in an inflator is generally uneconomic because the pressure vessels required to store the gas are bulky, heavy and expensive and the use of gas-generating propellants produces significant quantities of toxic gases, such as carbon monoxide, and/or flammable gases, such as hydrogen.
Hybrid inflators utilize a combination of stored gas and the products of combustion of pyrotechnic material to deploy an inflatable system. The gas is stored in a chamber at a relatively high pressure. The chamber where the gas is stored is adjacent to a combustion chamber that contains an initiator and a pyrotechnic material for producing hot combustion gases that are delivered to the stored gas. The mixture of the hot combustion gases and stored gases are delivered through an outlet to inflate an inflatable component. Hybrid inflators are particularly useful in that no azide is required in the inflatable system and that complex filters are not required to cool and clean the gases. Examples of hybrid inflators are disclosed in U.S. Pat. No. 5,670,738 (a hybrid inflator using compressed gas together with an initiator and a pyrotechnic gas generator), U.S. Pat. No. 5,660,412 (a hybrid inflator consisting of a pressure vessel containing a main charge of pyrotechnic material and a secondary charge of pyrotechnic material, wherein the secondary charge produces products of combustion that ignite the main charge), U.S. Pat. No. 5,588,676 (a hybrid inflator with a pyrotechnic gas generator and a gas chamber storing pressurized gas), U.S. Pat. No. 5,462,307 (a hybrid airbag inflator with a first chamber containing compressed gas and a second chamber containing an igniter and pyrotechnic material) and U.S. Pat. No. 5,131,680 (an inflator assembly which includes pyrotechnic material and a container of gas under pressure). Each of the above mentioned patent is incorporated herein by reference.
Distributed charge inflators generally include a distributed gas-generating material, that may have a faster burning center core ignition material surrounded by supplemental propellant, or use a homogenous mixture of ignition material and propellant, and also include an initiator (e.g., an electronic squib) used to ignite the gas generating material upon a signal from an initiating device. The fast burning gas generating material or “distributed charge” is designed to be installed within and distributed along the interior of the undeployed inflatable component itself. It is not necessary to contain the distributed charge within any type of exterior housing or assembly.
FIG. 1 shows a distributed charge inflator installed within an inflatable system disclosed in U.S. Pat. No. 6,062,143, which is assigned to the assignee of the present application and is incorporated herein by reference. As shown, inflatable system 4 includes a inflatable component 3 and a distributed charge inflator. The distributed charge inflator includes a distributed charge 14, a sheath 17 and an initiator 11. Distributed charge 14 is distributed within the inflatable component 3. Inflatable system 4 receives an electric signal from an activator 1 along a wire 2, when a crash sensor or other activator determines that the inflatable component must be deployed. Upon receiving a signal from a sensor, initiator 11 ignites distributed charge 14. The combustion of distributed charge 14 generates a gas and inflates an inflatable component 3.
Because the distributed charge is distributed, rather than confined to a small enclosed container or chamber as in the prior art systems listed above, it generates gases and releases the generated gases with far less explosive force than in the prior art systems. The distributed charge inflator system virtually eliminates the uneven inflations, pressure waves, and inertial effects of gases injected into the inflatable components from externally located gas generators. Also, the distributed charge inflator equipped inflatable restraints deploy less aggressively than existing systems because the energy of the expanding gases is essentially distributed uniformly throughout the inflatable structure during deployment.
Further, because the distributed charge is distributed internally within the inflatable component, there is no necessity to reinforce the inflatable fabric or bladder material against pressure, heat and high velocity particulates at the point at which gases would have been forcefully injected into the inflatable component from the gas generator external to the inflatable component.
The distributed charge inflator is not limited to simply propagating the rapid ignition of other materials, the burning of which then produces the quantities of gas necessary to inflate a given structure. The distributed charge inflator system is a complete, autonomously-operating inflation system.
Example of inflatable components which the distributed charge inflator can be used to inflate are described in U.S. Pat. No. 5,282,648 (body and head restraints); U.S. Pat. No. 5,322,322 (side impact head strike protection); U.S. Pat. No. 5,480,181 (side impact head strike protection); and U.S. Pat. No. 5,464,246 (tubular cushions), which are incorporated herein by reference, as well as automotive airbags and other inflatable products.